Williams, who was driving alone at the time of the accident, underwent knee surgery Saturday at Orlando Regional Medical Center.
According to police reports, the accident happened when an oncoming driver swerved into her lane. The driver was said to have been having a seizure at the time.
For Williams, this latest incident follows up one in 1994, when she was hit in the neck by a stray bullet while at an LPGA Tour event in Ohio.
While she was not severely injured then, she will certainly be absent from the women's tour for an extended period following this most recent of accidents.